Radio communication apparatus and transmission power control method

ABSTRACT

Desired signal power measured at a desired signal power measuring circuit  105  is averaged over a plurality of slots by an averaging circuit  106  to reduce a power error in desired signal power of each slot. An SIR measuring circuit  108  calculates SIR(n) of each slot from the average value of desired signal power in the plurality of slots and the measured value of interference signal power of each slot, and a TPC generating circuit  109  makes a comparison between SIR(n) of each slot and a threshold value, and generates transmission power control information. This makes it possible to control transmission power for each slot with high accuracy in asymmetrical communication.

TECHNICAL FIELD

The present invention relates to a radio communication apparatus and atransmission power control method, which are used in a radiotransmitting system such as a mobile phone, a cellular phone and thelike.

BACKGROUND ART

In a radio transmitting system such as a mobile phone, a cellular phoneand the like, an SIR (Signal to Interference Ratio) is fixed andtransmission power control is carried out in accordance with the stateof each transmission channel in order to maintain a BER (Bit Error Rate)at a value below a predetermined value.

The transmission power control method includes a closed looptransmission power control and an open loop transmission power control.

The closed loop transmission power control is a method for controllingtransmission power based on the contents of a TPC (Transmit PowerControl) command where SIR corresponding to reception quality of atransmitting signal from one end is measured at the other end ofcommunication and the TPC command, which reduces transmission power whena measured SIR value is higher than a target SIR value and whichincreases transmission power when the measured SIR value is lower thanthe target SIR value, is transmitted through an inverse channel.

On the other hand, the open loop transmission power control is a methodfor controlling a transmission power value in such a way that areception level is subtracted from the known transmission level of theother end of communication to calculate a level lost in a radio sectionand a target reception level of the other end of communication is addedto the lost level.

Here, data communication in which the information amount of a forwardlink is greatly larger than that of a reverse link is expected to bemainstream in the future, and the development of a radio communicationsystem of asymmetrical communication where the information amount of thereverse link is asymmetrical with respect to that of the forward link isproceeding.

In the case of the radio communication system where the informationamount of the reverse link is symmetrical with respect to that of theforward link, since a time difference between transmission timing andreception timing is small, transmission power can be controlled for eachslot with high accuracy.

However, in the radio communication system that performs asymmetricalcommunication where a time difference between transmission timing andreception timing becomes large, a method for controlling transmissionpower for each slot with high accuracy has not been disclosed yet.

DISCLOSURE OF INVENTION

It is an object of the present invention to provide a radiocommunication apparatus and a transmission power control method capableof controlling transmission power for each slot with high accuracy inasymmetrical communication.

The above object can be attained by averaging desired signal power overa plurality of slots to reduce a power error in desired signal power inthe respective slots and to improve precision of measurement.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram illustrating the configuration of a radiocommunication apparatus according to a first embodiment of the presentinvention;

FIG. 2 is a block diagram illustrating the configuration of a radiocommunication apparatus as a communication partner with respect to theradio communication apparatus of the first embodiment of the presentinvention;

FIG. 3 is a block diagram illustrating the configuration of a radiocommunication apparatus according to a second embodiment of the presentinvention; and

FIG. 4 is a block diagram illustrating the configuration of a radiocommunication apparatus as a communication partner with respect to theradio communication apparatus of the second embodiment of the presentinvention.

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiments of the present invention will be specifically explained withreference to the drawings accompanying herewith.

First Embodiment

The first embodiment explains the case of the closed loop transmissionpower control. FIG. 1 is a block diagram illustrating the configurationof a radio communication apparatus according to the first embodiment ofthe present invention.

A duplexer 102 switches a channel through which a signal passes at atransmitting time and a receiving time and outputs a signal receivedfrom an antenna 101 to a reception RF circuit 103, and outputs atransmitting signal outputted from a transmission RF circuit 112 to theantenna 101.

The reception RF circuit 103 amplifies the received signal,frequency-converts the amplified signal to a baseband, and outputs theresultant to a demodulating circuit 104. The demodulating circuit 104demodulates the baseband signal to extract received data of the radiocommunication apparatus.

A desired signal power measuring circuit 105 measures reception power(hereinafter referred to as “desired signal power”) of a known signalincluded in the output signal of the demodulating circuit 104, andoutputs a measuring result to an averaging circuit 106. The averagingcircuit 106 calculates an average value of desired signal power in aplurality of slots, and outputs the average value to an SIR measuringcircuit 108.

Here, in the case where a known signal sequence is long and aninterference signal can be suppressed and the slots are close to eachother and variations in reception power due to fading is small, desiredsignal power in the respective slots is substantially equal to eachother. Accordingly, the calculation of the average value of desiredsignal power in the respective slots makes it possible to improveaccuracy of measurement in desired signal power.

An interference signal power measuring circuit 107 measures power of aninterference signal outputted from the demodulating circuit 104, andoutputs a measuring result to the SIR measuring circuit 108.

The SIR measuring circuit 108 calculates SIR(n) (n indicates slotnumber) of each slot from the average value of desired signal power inthe plurality of slots and the measured value of interference signalpower of each slot, and outputs the resultant to a TPC generatingcircuit 109.

The TPC generating circuit 109 makes a comparison between SIR(n) of eachslot and a threshold value, and generates transmission power controlinformation, which instructs the slot whose SIR(n) is lower than thethreshold value to increase transmission power, and generatestransmission power control information, which instructs the slot whoseSIR(n) is higher than the threshold value to reduce transmission power.After that, the TPC generating circuit 109 outputs generatedtransmission power control information of each slot to a multiplexingcircuit 110.

The multiplexing circuit 110 multiplexes a plurality of pieces oftransmission power control information into one slot transmitting dataand outputs the resultant to a modulating circuit 111. The modulatingcircuit 111 modulates an output signal of the multiplexing circuit 110,and outputs the modulated signal to a transmission RF circuit 112. Thetransmission RF circuit 112 converts the frequency of an output signalof the modulating circuit 111, amplifies transmission power, andtransmits the amplified transmission power as a radio signal from theantenna 102 through a duplexer 102.

FIG. 2 is a block diagram illustrating the configuration of a radiocommunication apparatus as a communication partner with respect to theradio communication apparatus of FIG. 1.

A duplexer 202 switches a channel through which a signal passes at atransmitting time and a receiving time and outputs a signal receivedfrom an antenna 201 to a reception RF circuit 203, and outputs atransmitting signal outputted from a transmission RF circuit 208 to theantenna 201.

The reception RF circuit 203 amplifies the received signal,frequency-converts the amplified signal to a baseband, and outputs theresultant to a demodulating circuit 204. The demodulating circuit 204demodulates the baseband signal and outputs the demodulated signal to anisolating circuit 205. The isolating circuit 205 isolates an outputsignal of the demodulating circuit 204 into received data andtransmission power control information.

A CL (Closed Loop) transmission power control circuit 206 controls anincrease or decrease in transmission power at the transmitting FRcircuit 112 based on transmission power control information isolated atthe isolating circuit 205.

A modulating circuit 207 modulates transmitting data and outputs it tothe transmitting RF circuit 208. The transmitting RF circuit 208converts the frequency of the output signal of the modulating circuit207 and amplifies transmission power based on control of the CLtransmission power control circuit 206, and transmits it as a radiosignal from the antenna 201 through the duplexer 202.

Thus, desired signal power is averaged over the plurality of slots andthe closed loop transmission power control is performed using theaverage value, making it possible to reduce a power error in desiredsignal power in the respective slots and to improve precision ofmeasurement. This also makes it possible to control transmission powerfor each slot with high accuracy in the closed loop transmission powercontrol of asymmetrical communication.

Second Embodiment

The second embodiment will explain the case of the open looptransmission power control having an outer loop that controls referencepower for transmission power control. FIG. 3 is a block diagramillustrating the configuration of a radio communication apparatusaccording to the second embodiment of the present invention. In theradio communication apparatus illustrated in FIG. 3, the same referencenumerals as those of FIG. 1 are added to the configuration portionshaving the same operations as those of the radio communication apparatusillustrated in FIG. 1, and the explanation is omitted.

The radio transmission apparatus illustrated in FIG. 3 adopts theconfiguration in which an error correcting/decoding circuit 301, a CRCdeciding circuit 302, and a transmission power deciding circuit 303 areadded to the radio communication apparatus illustrated in FIG. 1.

The error correcting/decoding circuit 301 provides errorcorrecting/decoding processing to an output signal of the demodulatingcircuit 104, and extracts received data. The CRC deciding circuit 302performs a CRC decision to the output signal of the demodulating circuit104. The transmission power deciding circuit 303 calculates atransmission reference power value SIRt of a communication partner usinga CRC decision value outputted from the transmission power decidingcircuit 303 as a reference of reception quality.

Here, generally, in the case of performing transmission using aplurality of transmission slots, in order to scatter the positions ofthe error bits to improve an error correction capability, interleave isperformed in such a way that transmitting signals of all slots arearranged at random. In this case, the radio communication apparatustransmits a signal indicative of transmission reference power value SIRtto the communication partner to make it possible to control transmissionpower of the communication partner such that the reception qualitysubjected to error correction processing in all slots satisfies apredetermined quality.

The radio communication apparatus, however, cannot excise control to thecommunication partner in response to interference amount of each slotusing only transmission reference power value SIRt. This cannot reducetransmission power with respect to the slot whose interference amount issmall, with the result that interference with other cells cannot bereduced.

In order to solve the above problem, the transmission power decidingcircuit 303 of the radio communication apparatus adds SIR(n) of eachslot to the calculated transmission reference power value SIRt tocalculate a transmission reference power value SIRt(n) of each slot.

The multiplexing circuit 110 multiplexes information indicative oftransmission reference power value SIRt(n) to transmitting data, andoutputs the resultant to the modulating circuit 111.

FIG. 4 is a block diagram illustrating the configuration of a radiocommunication apparatus as a communication partner with respect to theradio communication apparatus of FIG. 3. In the radio communicationapparatus illustrated in FIG. 4, the same reference numerals as those ofFIG. 2 are added to the configuration portions having the sameoperations as those of the radio communication apparatus illustrated inFIG. 2, and the explanation is omitted.

The radio transmission apparatus illustrated in FIG. 4 adopts theconfiguration in which a desired signal power measuring circuit 401 forthe CL transmission power control circuit 206 and an OL (Open Loop)transmission power control circuit 402 are added as compared with theradio communication apparatus illustrated in FIG. 2.

The isolating circuit 205 isolates the output signal of the demodulatingcircuit 204 into received data and a transmission reference powercontrol value SIRt(n).

The desired signal power measuring circuit 401 measures desired signalpower S of the known signal included in the output signal of thedemodulating circuit 204, and outputs the measuring result to the OLtransmission power control circuit 402. The OL transmission powercontrol circuit 402 calculates transmission power T(n) of each slot byequation (1) shown below and controls an increase or decrease intransmission power at the transmitting RF circuit 208. It is noted thatConst in equation (1) is a fixed value for gain control.T(n)=SIRt(n)−S+Const  (1)

Thus, the open loop transmission power control is performed withconsideration given to SIR of each slot in addition to the transmissionreference power value, making it possible to control transmission powerfor each slot with high accuracy in asymmetrical communication.

As explained above, according to the radio communication apparatus andthe transmission power control method of the present invention, sincethe power error in desired signal power of each slot is reduced to makeit possible to improve accuracy in measurement, transmission power canbe controlled for each slot with high accuracy in asymmetricalcommunication.

This application is based on the Japanese Patent Application No. HEI11-286317 filed on Oct. 7, 1999, entire content of which is expresslyincorporated by reference herein.

INDUSTRIAL APPLICABILITY

The present invention is suitable for use in a base station apparatus ofa radio transmission system or a communication terminal apparatus.

1. A radio communication apparatus that performs asymmetricalcommunication, the apparatus comprising: a desired signal power measurerthat measures individual desired signal reception powers of a pluralityof slots; an averager that calculates an average value of the individualdesired signal reception powers of the plurality of slots; aninterference signal power measurer that measures individual interferencesignal reception powers of the plurality of slots; an SIR measurer thatmeasures individual reception qualities of the plurality of slots, ineach slot a reception quality being measured based on the average valueof the individual desired signal reception powers and one of theindividual interference signal powers corresponding to said each slot; apower control information generator that generates individualtransmission power control information corresponding respectively to theplurality of slots, based on the individual reception qualities of saidplurality of slot; and a transmitter that transmits the individualtransmission power control information corresponding respectively to theplurality of slots, in a single slot.
 2. A radio communication apparatusthat performs asymmetrical communication with the radio communicationapparatus of claim 1, said radio communication apparatus comprising: anisolator that isolates, from a received signal, the individualtransmission power control information corresponding respectively to theplurality of slots; a transmission power controller that controlsindividual transmission powers of the plurality of slots based on theindividual transmission power control information correspondingrespectively to said plurality of slots; and an amplifier that amplifiestransmitting data in accordance with the control of the transmissionpower controller.
 3. A radio communication apparatus that performsasymmetrical communication, the apparatus comprising: a desired signalpower measurer that measures individual desired signal reception powersof a plurality of slots; an averager that calculates an average value ofthe individual desired signal reception powers of the plurality ofslots; an interference signal power measurer that measures individualinterference signal reception powers of the plurality of slots; an SIRmeasurer that measures individual reception qualities of the pluralityof slots, in each slot a reception quality being measured based on theaverage value of the individual desired signal reception powers and oneof the individual interference signal powers corresponding to said eachslot; a reference power calculator that calculates individual referencetransmission powers of the plurality of slots based on an overallreception quality of the plurality of slots and the individual receptionqualities of said plurality of slots; and a transmitter that transmitsindividual reference transmission power control informationcorresponding respectively to the plurality of slots, in a single slot.4. The radio communication apparatus according to claim 3, wherein thereference power calculator calculates a reference transmission power ofa slot by adding the overall reception quality of the plurality of slotsand one of the individual reception qualities of the plurality of slotscorresponding to said slot.
 5. The radio communication apparatus ofclaim 3, wherein the reference power calculator calculates the overallreception quality of the plurality of slots based on individual CRCcheck results of said plurality of slots.
 6. A radio communicationapparatus that performs asymmetrical communication with the radiocommunication apparatus of claim 3, said radio communication apparatuscomprising: an isolator that isolates, from a received signal, theindividual reference transmission power information correspondingrespectively to the plurality of slots; a transmission power controllerthat controls individual transmission powers of the plurality of slotsbased on the individual reference transmission power informationcorresponding respectively to said plurality of slots; and an amplifierthat amplifies transmitting data in accordance with the control of thetransmission power controller.
 7. A base station apparatus that performsasymmetrical communication, the apparatus comprising; a desired signalpower measurer that measures individual desired signal reception powersof a plurality of slots; an averager that calculates an average value ofsaid individual desired signal reception powers of the plurality ofslots; an interference signal power measurer that measures individualinterference signal reception powers of the plurality of slots; an SIRmeasurer that measures individual reception qualities of the pluralityof slots, in each slot a reception quality being measured based on theaverage value of the individual desired signal reception powers and oneof the individual interference signal powers corresponding to said eachslot; a power control information generator that generates individualtransmission power control information corresponding respectively to theplurality of slots, based on the individual reception qualities of saidplurality of slots; and a transmitter that transmits the individualtransmission power control information corresponding respectively to theplurality of slots, in a single slot.
 8. A communication terminalapparatus that performs asymmetrical communication, the apparatuscomprising: a desired signal power measurer that measures individualdesired signal reception powers of a plurality of slots; an averagerthat calculates an average value of said individual desired signalreception powers of the plurality of slots; an interference signal powermeasurer that measures individual interference signal reception powersof the plurality of slots; an SIR measurer that measures individualreception qualities of the plurality of slots, in each slot a receptionquality being measured based on the average value of the individualdesired signal reception powers and one of the individual interferencesignal powers corresponding to said each slot; a reference powercalculator that calculates individual reference transmission powers ofthe plurality of slots based on an overall reception quality of theplurality of slots and the individual reception qualities of saidplurality of slots; and a transmitter that transmits individualreference transmission power control information correspondingrespectively to the plurality of slots, in a single slot.
 9. Atransmission power control method in a plurality of radio communicationapparatuses that perform asymmetrical communication, said methodcomprising: in one of the plurality of communication apparatuses;measuring individual desired signal reception powers of a plurality ofslots; calculating an average value of the individual desired signalreception powers of the plurality of slots; measuring individualinterference signal reception powers of the plurality of slots;generating individual transmission power control informationcorresponding respectively to the plurality of slots, for each slot theindividual transmission power control information being generated basedon the average value of the individual desired signal reception powersand one of the individual interference signal powers corresponding tosaid each slot; and transmitting the individual transmission powercontrol information corresponding respectively to the plurality ofslots, in a single slot, and in another one of the plurality of radiocommunication apparatuses: isolating, from a received signal, theindividual transmission power control information correspondingrespectively to the plurality of slots; and amplifying individualtransmission powers of a plurality of transmitting slots based on theindividual transmission power control information correspondingrespectively to the plurality of slots.
 10. A transmission power controlmethod in a plurality of radio communication apparatuses that performasymmetrical communication, said method comprising: in one of theplurality of radio communication apparatuses: measuring an overallreception quality of a plurality of slots; measuring individualreception qualities of the plurality of slots; calculating individualreference transmission powers of the plurality of slots based on theoverall reception quality of the plurality of slots and the individualreception qualities of said plurality of slots; and transmittingindividual reference transmission power information correspondingrespectively to the plurality of slots, in a single slot, and in anotherone of the plurality of radio communication apparatuses: isolating, froma received signal, the individual reference transmission powerinformation corresponding respectively to the plurality of slots; andamplifying individual transmission powers of a plurality of transmittingslots based on the individual reference transmission power informationcorresponding respectively to the plurality of slots.